WASHINGTON, April 7 - U.S. Secretary of State John Kerry told Russian Foreign Minister Sergei Lavrov on Monday that Washington was watching events in eastern Ukraine with great concern and any moves by Moscow to destabilize Ukraine would "incur further costs for Russia," Reuters reported.

State Department spokeswoman Jen Psaki said that in the telephone call Kerry "called on Russia to publicly disavow the activities of separatists, saboteurs and provocateurs" in Ukraine.